MB-100 Fix typo in log message.

Change-Id: I63fdf21eeec46c44191087e5d768edd4538216b9
Reviewed-on: http://review.couchbase.org/28865
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>